FBI Director William H. Webster said yesterday that he supports capital punishment as the maximum penalty for presidential assassinations, but agreed that Congress might have to redraft current law to withstand court challenge.

"I think it would be perceived as a deterrent," Webster said of the death penalty during testimony before the House Assassinations Committee. "I don't have any problems with capital punishment on the assassination of a president."

The FBI director made his remarks under questioning by Rep. Christopher J. Dodd (D-Conn.). While federal assassination laws passed in the wake of President Kennedy's murder provide for the death penalty, Dodd said court rulings in recent years might make it unconstitutional.

In particular, Dodd cited a 1977 decision of the U.S. 5th Circuit Court of Appeals which held invalid the federal death penalty statute to which the assassination laws are tied.

"It certainly raises serious questions as to whether a court could impose that punishment," Dodd said.

FBI Director Webster and CIA Deputy Director Frank Carlucci appeared before the committee to review the government's capacity to deal with political assassinations in light of the 1963 murder of President Kennedy and the 1968 killing of the Rev. Martin Luther King Jr.

Webster said the FBI's current investigation into the killing of Rep. Leo J. Ryan (E-Calif.) last month in Guyana offers a good illustration of how the bureau's "major case plan" works in such cases. He said he has been egtting oral and written reports each day from a network of government command posts, including three set up by the FBI -- in Dover, Del.; Charleston, S.C., and San Francisco.

"Depending on the seriousness and complexity of the case, our response could vary," Webster said. "But whatever the extent of our investigation, it will be as thorough and well-ordered as we are capable of making it."

The FBI has identified the nine gunmen who allegedly killed Ryan and four others after a visit to the Peoples Temple camp in Jonestown, Guyana, and eight of them are dead, Webster said. The ninth is in custody in Guyana. Asked what the FBI could do in response to reports that cult members might try to assassinate political leaders, the FBI chief said: "The only way to deal with that particular type of alleged hit list would be to declare martial law. I don't think that would be acceptable."

In the event of a presidential assassination, Webster said the FBI would work with the Secret Service to "freeze the scene" immediately. The Armed Forces Institute of Pathology would arrange for an autopsy. The FBI would take custody of all physical evidence obtained.

CIA deputy diector Carlucci said that "by far the most important thing CIA can do in the sordid business of assassinations is to help prevent them." He said he could not go into deatils, but he assured the committee that "there are public figures alive in this world today who have CIA to thank for it."

Carlucci said he could not conceive of the CIA's failing to provide the FBI with all the information it might have, bearing on a future presidential assassination, but Rep. Floyd Fithian (D-Ind.) still had his doubts. He said the CIA would have said the same thing before Kennedy's assassination.